Adaptive, multi-channel teleconferencing system

ABSTRACT

A method is disclosed to determine the presence of one or more cellular phones in the same sound field as an endpoint that is dedicated for teleconferencing, such as a speakerphone. The teleconference bridge of the illustrative embodiment continually receives geo-location information about the cell phone. Based on the geo-location of the cell phone relative to the position of the speakerphone, the bridge determines whether to include or exclude signals that are received from the cell phone when preparing a signal for transmission to the speakerphone during a conference call. The bridge also determines whether to refrain from transmitting an audio signal to the cell phone, when the bridge infers that the cell phone is being used as a satellite microphone, such as when the cell phone is placed on a conference room table. As a result, each conference call participant is able to use his or her own cell phone as a personal satellite microphone, which can improve the sound quality of the conference call.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of:

-   -   (1) U.S. Patent Application Ser. No. 60/895,563, filed on Mar.        19, 2007,        which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to telecommunications in general, and,more particularly, to an improved teleconferencing system.

BACKGROUND OF THE INVENTION

FIG. 1 depicts a schematic diagram of teleconference system 100 in theprior art. System 100 comprises telecommunications endpoints 101-1through 101-J, wherein J is an integer greater than one; private branchexchange (PBX) 102; telecommunications network 103; and teleconferencebridge 104, interconnected as shown.

Telecommunications endpoint 101-j, where j has a value between 1 and J,inclusive, is capable of handling a telephone call for its user.Endpoint 101-j is able to call, or to be called by, another endpoint. Inorder to participate in a conference call, endpoint 101-j is able todial a telephone number that routes to teleconference bridge 104.Endpoint 101-j can be a cellular phone, a conference phone (i.e.,“speakerphone”), a deskset, or some other type of telecommunicationsappliance.

Some of endpoints 101-1 through 101-J are PBX terminals, such as thosein an office enterprise network, for which telecommunications service isenabled by private branch exchange 102.

Telecommunications network 103 provides the connectivity among endpoints101-1 through 101-J, exchange 103, and teleconference bridge 104.Telecommunications network 103 comprises a transmission network—forexample, the Public Switched Telephone Network, which is a complex oftelecommunications equipment that is owned and operated by differententities throughout the World. Network 103 can also comprise theInternet or possibly other Internet Protocol-based networks.

Teleconference bridge 104 is a server or switch that enables the usersof multiple endpoints to communicate with each other during a conferencecall. Bridge 104 receives audio signals from endpoints that areparticipating on a conference call, mixes those signals together, andtransmits the mixed signals back to the endpoints.

As depicted in FIG. 1, system 100 is a traditional teleconferencingsystem for J teleconference locations, where a location is defined by asingle endpoint (i.e., endpoint 101-j), supported by a teleconferencebridge (i.e., bridge 104). Some of the endpoints are speakerphones,which are designed specifically to handle conference call communication.Each speakerphone is connected to the bridge via a monophonic,bi-directional channel. If any given speakerphone at a teleconferencelocation has multiple feeds—that is, a main microphone and one or moresatellite microphones, or a main loudspeaker and one or more satelliteloudspeakers—they are combined at the speakerphone itself into themonophonic channel transmitted by that speakerphone to the bridge. Thisis depicted in FIG. 2, showing an overhead view in which endpoint 101-11is situated on table 202 of conference room 201. Endpoint 101-11, aspeakerphone, comprises satellite microphones 203-1 and 203-2, as wellas loudspeaker 204.

During operation, the monophonic feed from each endpoint, such asendpoint 101-11, is fed into bridge 104, which adds the feeds, and thesum is distributed by the bridge back to the speakerphones at the otherlocations. Each speakerphone at each location receives a signal via amonophonic channel from the bridge, which signal is played out of allloudspeakers connected to that speakerphone. In the operation of anysuch traditional bridge, the monophonic signal received by any endpoint101-j contains components of one or more other endpoints 101-k, k≠j, butexplicitly excludes components of the signal sent to the bridge byendpoint 101-j. By doing so, bridge 104 prevents regenerative acousticfeedback that would otherwise occur.

Each monophonic, bi-directional channel is associated with a phone linethat terminates at the conference bridge. From the bridge's perspective,each channel and line equates to a different “location,” even thoughconference call participant who are using a speakerphone and aparticipant who is using a cell phone might be present in the sameconference room.

SUMMARY OF THE INVENTION

The present invention breaks the “one line, one location” paradigm ofteleconferencing in the prior art. The teleconference bridge in theillustrative embodiment is able to utilize more than one audio channelfrom each location, where there are multiple signal sources present inthe room. For example, a participant's cell phone can be used as asatellite microphone to augment or replace the speakerphone's microphoneat the same location, for the purpose of improving the audio qualityexperienced on the conference call. As another example, more than onedeskset endpoint can be situated in a conference room, each with its ownport at the teleconference bridge of the illustrative embodiment; thebridge can mix the audio signals coming from and going to the multipledesksets in a way that optimizes audio quality and avoids acousticfeedback between participating phones located within the same acousticspace.

A key aspect of the illustrative embodiment is determining the presenceof one or more cellular phones that are in the same sound field as anendpoint that is dedicated for teleconferencing, such as a speakerphone.In accordance with the illustrative embodiment, the bridge continuallyreceives geo-location information about the cell phone. Based on thegeo-location of the cell phone relative to the position of thespeakerphone, the bridge determines whether to include or excludesignals that are received from the cell phone when preparing a signalfor transmission to the speakerphone during a conference call. Thebridge also determines whether to refrain from transmitting an audiosignal to the cell phone, when the bridge infers that the cell phone isbeing used as a satellite microphone, such as when the cell phone isplaced on a conference room table. In some embodiments, the bridge alsoaccounts for the presence of other types of endpoints that can be movedin and out of the sound field.

In accordance with the illustrative embodiment of the present invention,each conference call participant is able to use his or her own cellphone as a personal satellite microphone, which can improve the soundquality of the conference call by reducing the distance between theparticipant's mouth and the nearest microphone. And because there is aseparate channel to the conference bridge from each cell phone, theconference bridge can do the mixing, adapt to changing input signals,and create a better quality output than experienced with some of theuncoordinated speakerphones in the prior art.

The illustrative embodiment of the present invention comprises:establishing, at a teleconference bridge, a first teleconference callthat involves at least a first endpoint assigned to a first port, asecond endpoint assigned to a second port, and a third endpoint assignedto a third port, wherein first endpoint is capable of having a telephonecall independently of the teleconference bridge, and wherein the secondendpoint and the third endpoint are acoustically isolated from eachother; receiving, at the teleconference bridge, a first receive audiosignal s₁ from the first endpoint via the first port, a second receiveaudio signal s₂ from the second endpoint via the second port, and athird receive audio signal s₃ from the third endpoint via the thirdport; determining whether to transmit any audio signal that is based onat least one of the signal s₂ and the signal s₃ to the first endpoint,based on i) the terminal type of the first endpoint and ii) whether thefirst endpoint is acoustically collocated with the second endpoint; andtransmitting a first transmit audio signal x₁ to the third endpoint,wherein the signal x₁ is based on at least one of the signal s₁ and thesignal s₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of teleconference system 100 in theprior art.

FIG. 2 depicts an overhead view of conference room 201, as well astelecommunications endpoint 101-11 of system 100.

FIG. 3 depicts schematic diagram of the salient components ofteleconference system 300 in accordance with the illustrative embodimentof the present invention.

FIG. 4 depicts an overhead view of teleconference location 310-2, aswell as telecommunications endpoints 301-4 and 301-5 of system 300.

FIG. 5 depicts a block diagram of the salient components ofteleconference bridge 304, in accordance with the illustrativeembodiment of the present invention.

FIG. 6 depicts a flowchart of the overall salient tasks that are relatedto preparing for, establishing, and managing a teleconference call, asperformed by teleconference bridge 304, in accordance with theillustrative embodiment of the present invention.

FIGS. 7A through 7D depict some illustrative examples of how the numberof channels may vary across the teleconference locations, as related totask 601 in FIG. 6.

FIG. 8 depicts telecommunications endpoints 301-6, 301-7, and 301-8,some of which might be acoustically collocation with each other, asdetermined at task 602 of FIG. 6.

FIGS. 9A through 9D depict an overview of a chain of events that involvecell phone 301-4 being used by a participant to the conference call, asrelated to task 605 of FIG. 6.

FIG. 10 depicts a flowchart of the salient subtasks that are related toorganizing each teleconference location into receive audio channels andtransmit audio channels, as part of task 601.

FIG. 11 depicts a flowchart of the salient subtasks that are related todetermining acoustic collocation, as part of task 602.

FIG. 12 depicts a flowchart of the salient subtasks that are related toaccounting for cell phone or other portable endpoint, as part of task605.

FIG. 13 depicts a flowchart of the salient subtasks that are related toacoustically determining the presence of endpoints, as part of task 1001of FIG. 10.

FIG. 14 depicts a flowchart of the salient subtasks that are related todetermining which endpoints are acoustically collocated with endpoint301-j, as part of task 1103 of FIG. 11.

DETAILED DESCRIPTION

The following terms are defined for use in this Specification, includingthe appended claims:

-   -   The term “acoustic collocation,” and its inflected forms, is        defined as the state in which a first endpoint is receiving, via        its microphone, at least a component of a signal that has been        transmitted to a second endpoint and outputted via the second        endpoint's loudspeaker. When this occurs, the first endpoint is        said to be “acoustically collocated” with the second endpoint,        in addition to being in the same sound field as the second        endpoint. Note that in this case, the second endpoint might also        be acoustically collocated with the first endpoint, but not        necessarily.    -   The term “sufficient correlation,” and its inflected forms, is        defined as the state in which the teleconference bridge of the        illustrative embodiment transmits a first audio signal to a        second endpoint and receives back a second audio signal from a        first endpoint, and the received second signal resembles the        transmitted first signal closely enough to conclude that the        second signal is related to the first. Determining whether one        signal is “sufficiently correlated” with another is one way to        determine whether one endpoint is acoustically collocated with        another.    -   The term “acoustic isolation,” and its inflected forms, is        defined as the state in which a first teleconference location        (e.g., a conference room, the place where someone is        conferencing in from their cell phone, etc.) is sufficiently        distant from other teleconference locations such that the first        location does not acoustically interfere with or is not        acoustically interfered on by the other locations during a        conference call. The two teleconference locations are said to be        in different sound fields from each other.

FIG. 3 depicts schematic diagram of the salient components ofteleconference system 300 in accordance with the illustrative embodimentof the present invention. System 300 comprises telecommunicationsendpoints 301-1 through 301-J, wherein J is an integer greater than one;private branch exchange (PBX) 302; telecommunications network 303; andteleconference bridge 304, interconnected as shown.

Telecommunications endpoint 301-j, where j has a value between 1 and J,inclusive, is capable of originating, receiving, or otherwise handling atelephone call for its user. Endpoint 301-j is able to call, or to becalled by, another endpoint. In order to participate in a conferencecall, endpoint 301-j is able to dial a telephone number that routes toteleconference bridge 304. Endpoint 301-j can be an analog telephone, anISDN terminal, a softphone, an Internet-Protocol phone, a cellularphone, a cordless phone, a PBX deskset, a conference phone (i.e.,“speakerphone”), or some other type of telecommunications appliance. Itwill be clear to those skilled in the art how to make and use endpoint301-j.

Some of endpoints 301-1 through 301-J are PBX terminals, such as thosein an office enterprise network, for which telecommunications service isenabled by private branch exchange 302, as is well-known in the art.

Telecommunications network 303 provides the connectivity among endpoints301-1 through 301-J, exchange 303, and teleconference bridge 304.Network 303 comprises the Public Switched Telephone Network, which is acomplex of telecommunications equipment that is owned and operated bydifferent entities throughout the World. In the United States ofAmerica, for example, the Public Switched Telephone Network (or “PSTN”)comprises an address space that is defined by ten digits, and,therefore, comprises 10 billion unique addresses or “telephone numbers.”The public switched telephone networks in other countries are similar.In some embodiments, network 303 comprises the Internet or possiblyother Internet Protocol-based networks, either in addition to or asopposed to the PSTN.

It will be clear to those skilled in the art, after reading thisspecification, how to make and use embodiments of the present inventionthat comprise various combinations of networks within teleconferencesystem 300, which networks are public or private, wired or wireless, andcircuit-based or packet-based.

Teleconference bridge 304 is a server or switch that enables the usersof multiple endpoints to communicate with each other during a conferencecall. Bridge 304 receives audio signals from endpoints that areparticipating on a conference call, mixes those signals together basedon the transfer function associated with each output channel, andtransmits the mixed signals back to the endpoints, in accordance withthe illustrative embodiment of the present invention. Bridge 304 isdescribed in detail below and with respect to FIG. 5.

As those who are skilled in the art will appreciate, the techniques ofthe illustrative embodiment can be implemented at a device other than ateleconference bridge or at a teleconference bridge that is other than aserver or switch.

FIG. 3 depicts the endpoints that are to participate, or areparticipating, in a particular conference call, which endpoints aresituated at locations 310-1 through 310-L, wherein L is an integergreater than one. Each location 310-l, where l has a value between 1 andL, inclusive, comprises at least one telecommunications endpoint 301-j,where j has a value between 1 and J, inclusive. One effect of having Jindependent endpoints distributed across L teleconference locations isshown in FIG. 4, which depicts an overhead view of a conference room.Situated on table 402 of teleconference location 310-2 aretelecommunications endpoints 301-4 and 301-5, each one an independentendpoint that is capable of placing and handling calls. For example,endpoint 301-4 might be the cell phone of someone participating on thecall, while endpoint 301-5 might be a conference room phone that issituated in the conference room at location 310-2.

FIG. 5 depicts a block diagram of the salient components ofteleconference bridge 304, in accordance with the illustrativeembodiment of the present invention. Bridge 304 comprises receiveinterface 501-1, transmit interface 501-2, processor 502, and memory503, interconnected as shown. Bridge 304 is capable of performing thetasks described below and with respect to FIGS. 6 through 14.

Receive interface 501-1 and transmit interface 502-2 comprise thecircuitry that enables bridge 304 to respectively receive signals fromand transmit signals to network 303, in well-known fashion. Inaccordance with the illustrative embodiment, bridge 304 receives andtransmits audio signals that are represented in Internet Protocolpackets, in well-known fashion. As those who are skilled in the art willappreciate, in some alternative embodiments bridge 304 receives andtransmits audio signals represented in a different format.

Processor 502 is a general-purpose processor that is capable ofreceiving information from receive interface 501-1, of executinginstructions stored in memory 503, of reading data from and writing datainto memory 503, and of transmitting information to transmit interface501-2. In some alternative embodiments of the present invention,processor 502 might be a special-purpose processor. Processor 502performs the audio mixing function at bridge 304, in accordance with theillustrative embodiment of the present invention. As part of the audiomixing function, processor 502 is able to take any input audio signalfrom any endpoint or other source and mix it into the composite outputaudio signal to be transmitted to a particular endpoint, for allendpoints to which audio signals are to be transmitted. The specificoutput signal to a given endpoint is based on the mixer transferfunction associated with that output signal, as determined in theillustrative embodiment.

Memory 503 stores the instructions and data used by processor 502, inwell-known fashion. Memory 503 might be any combination of dynamicrandom-access memory (RAM), flash memory, disk drive memory, and soforth.

In accordance with the illustrative embodiment, bridge 304 communicateswith each endpoint 301-j via a different communication port, as is knownin the art. As those who are skilled in the art will appreciate, theports can be implemented in software or in hardware, or both. It will beclear to those skilled in the art how to make and use teleconferencingsystems where an endpoint has its own port at bridge 304 or an endpointshares a port with another endpoint, or both.

In accordance with the illustrative embodiment, bridge 304 is able toreceive on M_(L) input channels from endpoints at the combinedteleconference locations and to transmit on N_(L) output channels toendpoints at those locations. The values of M_(L) and N_(L) can be equalto or different from each other; in other words, some endpoints might bemicrophone-only devices, some might be loudspeaker-only devices, andsome might comprise both microphones and loudspeakers. Bridge 304 iscapable of unidirectional communication with the microphone-only devicesor loudspeaker-only devices, and of bidirectional communication with thedevices comprising both a microphone and loudspeaker.

FIGS. 6 and 10 through 14 depict flowcharts of salient tasks that arerelated to preparing for, establishing, and managing a teleconferencecall, as performed by teleconference bridge 304, in accordance with theillustrative embodiment of the present invention. As those who areskilled in the art will appreciate, some of the tasks that appear in theflowcharts that follow can be performed in parallel or in a differentorder than that depicted. Moreover, those who are skilled in the artwill further appreciate that in some alternative embodiments of thepresent invention, only a subset of the depicted tasks are performed.

Referring now to FIG. 6, at task 601 bridge 304 organizes eachteleconference location 310-l into M_(l) receive channels and N_(l)transmit channels, and processes those channels accordingly. Inaccordance with the illustrative embodiment, when more than onemicrophone is present in the first sound field (i.e., M₁ is greater thanone), the microphones can be used to create a multi-channel effect(e.g., stereo, three-channel, etc.) in the other sound fields that areinvolved in a conference call. In preparation for the conference call,bridge 304 first determines that multi-channel imaging is possible bydetecting the existence of a first sound field with two or moremicrophones and a second sound field with two or more loudspeakers.

FIGS. 7A through 7D depict illustrative examples of how the number ofaudio channels may vary across the teleconference locations, as relatedto task 601, and as a result, how the mixing of the audio signals willvary between different pairs of teleconference locations. The depictedexamples are intended to provide an overview, while details that arerelated to task 601 are described below and with respect to FIG. 10.FIG. 7A depicts an example of where M₂ (i.e., the number of microphonesat location 310-2) is equal to N₄ (i.e., the number of loudspeakers atlocation 310-4), where M₂ and N₄ are equal to two. FIG. 7B depicts anexample of where M₂ (i.e., location 310-2 microphones) is less than N₃(i.e., location 310-3 loudspeakers); in this situation, bridge 304 mixesto a larger number of loudspeaker channels than microphone channels.FIG. 7C depicts an example of where M₄ (i.e., location 310-4microphones) is greater than N₅ (i.e., location 310-5 loudspeakers); inthis situation, bridge 304 mixes down to a smaller number of loudspeakerchannels than microphone channels. And in FIG. 7D, M₁ (i.e., the numberof microphones at location 310-1) is depicted as being equal to N₃(i.e., the number of loudspeakers at location 310-3), where M₁ and N₃are equal to three. It will be clear to those skilled in the art how tomake and use embodiments of the invention that involve otherteleconference locations with different numbers of microphones andloudspeakers than those depicted.

At task 602, bridge 304 determines for each location whether two aremore endpoints are acoustically collocated, and processes signals forthose endpoints accordingly. The purpose of doing so is to determinewhether the sound coming from the loudspeaker of any one endpoint willadversely feed back into the microphone of another. FIG. 8 depicts thispossibility of feedback, in which situated on table 802 ofteleconference location 310-3 are telecommunications endpoints 301-6,301-7, and 301-8, each one an independent endpoint that is capable ofhandling calls. For example, deskset endpoints 301-7 and 301-8 are closeenough that they might cause feedback problems with each other unlesstheir signals are conditioned; the same can be said of cell phone 301-6and deskset 301-7. At the same time, however, cell phone 301-6 anddeskset 301-8 might not cause feedback issues with each other, possiblybecause they are sufficiently separated. Although FIG. 8 is intended toprovide an example of acoustic collocation, details that are related totask 602 for determining acoustic collocation are described below andwith respect to FIG. 11.

At task 603, bridge 304 establishes a conference call in well-knownfashion. involving endpoints 301-1 through 301-J.

At task 604, bridge 304 during the conference call continually receivesaudio signals s₁ through s_(J) from endpoints 301-1 through 301-J, inwell-known fashion.

At task 605, bridge 304 determines whether one or more endpoints areappearing at or disappearing from one or more of the teleconferencelocations, and processes signals for those endpoints accordingly. Theseendpoints of interest can be cell phones, other types of mobile orportable endpoints, or normally stationary endpoints (e.g., desksets,etc.) that are suddenly plugged into the call at an existingteleconference location. Bridge 304 monitors endpoints because they canconceivably wander in and out of a sound field (or sound fields)involved in the call, as described in the following scenario describedwith respect to FIG. 9, and possibly affect the audio qualityexperienced by the participants.

FIGS. 9A through 9D depict an overview of a chain of events as relatedto task 605 that involve endpoint 301-4, a cell phone, being used by aparticipant of the conference call. Note that details that are relatedto task 605 are described below and with respect to FIG. 12. In thissequence of events, bridge 304 monitors cell phone 301-4. As depicted inFIG. 9A, the participant approaches teleconference location 310-2. Whenbridge 304 determines that cell phone 301-4 is present in location310-2's sound field, the bridge adjusts the signals that it transmits toboth cell phone 301-4 and to other endpoints in the sound field such asendpoint 301-5, a conference phone. As depicted in FIG. 9B, the attendeethen puts her cell phone on the table in front of her (i.e., on table902). At this point, the cell phone's microphone is used as a satellitemicrophone, and there is no need to feed back the audio signals of theconference call to cell phone 301-4. The output of bridge 304 is fed tothe loudspeaker of the stand-alone conference phone in the room, namelyendpoint 301-5. As depicted in FIG. 9C, the cell phone user gets up andwalks around the room, carrying her cell phone, in which case bridge 304compensates by possibly resuming the feeding of audio to cell phone301-4. And as depicted in FIG. 9D, the cell phone user then leaves theroom, possibly to go to another teleconference location that is part ofthe same conference call in another part of the building; in response,bridge 304 starts feeding the audio signal from the cell phone user toendpoint 301-5.

As shown by FIGS. 9A through 9D, teleconference bridge 304 is able toadapt to the changing relationship between microphones/loudspeakers andlocations. Thus, if the attendee decides to leave the room, she can takeher cell phone with her and continue participating on the conferencecall. And if bridge 304 previously was not feeding an output signal tothe cell phone, because feeding the signal to the stand-aloneloudspeaker was sufficient, the bridge can then start feeding the outputsignal to the cell phone when the bridge detects that the phone ismoving out of the room and away from the loudspeaker.

At task 606, bridge 304 during the conference call continually transmitsaudio signals x₁ through x_(J) to endpoints 301-1 through 301-J, inwell-known fashion. The transmitted signals are based on variousadjustments to the mixer transfer functions that are associated with theoutput channels, each transfer function being adjusted at one or more oftasks 601, 602, and 605 in accordance with the illustrative embodimentof the present invention. Specifically, each transmitted signal can bebased on one or more receive signals (i.e., s₁ through s_(J)), on adetermination that a first endpoint is acoustically collocated with asecond endpoint, on two signals being sufficiently correlated with eachother, or on something else that affects the output signal's transferfunction. Bridge 304 can exclude at least a component of one or morereceive signals from a transmitted signal or can refrain fromtransmitting a signal entirely.

At task 607, bridge 304 refrains from transmitting an audio signal toone or more endpoints of interest that the bridge at task 605 determinedwere present, based on the criteria applied at task 605.

At task 608, bridge 304 determines whether the conference call hasfinished. If not, task execution proceeds back to task 604. If the callhas finished, task execution ends.

FIG. 10 depicts a flowchart of the salient subtasks that are related toorganizing each teleconference location into receive audio channels andtransmit audio channels, as part of task 601, in accordance with theillustrative embodiment of the present invention.

At task 1001, bridge 304 determines the presence of endpoints that areto participate in a conference call, as well as the relative positionsof the endpoints at each teleconference location. In accordance with theillustrative embodiment, this determination is achieved acoustically, asdescribed below and with respect to FIG. 13.

As those who are skilled in the art will appreciate, in some alternativeembodiments bridge 304 can determine the presence of endpoints atteleconference locations and the endpoints' relative positions via othermeans. A first alternative means comprises receiving a calling numberidentifier from each endpoint that is calling into the conference calland looking up the identifier in a database that comprises informationon the endpoints, as well as on their teleconference locations andrelative positions at each location. A second alternative meanscomprises receiving information that is spoken or entered (e.g., viaendpoint keypad, etc.) from each endpoint at the participatinglocations, where the information received from an endpoint describes theteleconference location and relative position of that endpoint and ofpossibly other endpoints. And a third alternative means comprisesapplying the technique of using geo-location measurements that isdescribed below and with respect to task 1202.

Based on the determined relative positions of the endpoints, bridge 304then creates, for each teleconference location 310-l, P_(l) audio inputchannels from and Q_(l) audio output channels to location 310-l. Forexample, if a first subset of endpoints at location 310-l appear to besituated on the left side of a conference room, a second subset appearto be on the right side, and a third subset appear to be in the middle,then bridge 304 creates a “left” channel, a “right” channel, and a“middle” channel, respectively.

At task 1002, bridge 304 assigns each endpoint at each teleconferencelocation to one of the audio channels created at task 1001. Eachteleconference location 310-l comprises M_(l) microphones and N_(l)loudspeakers that are assigned to P_(l) input channels and Q_(l) outputchannels associated with location 310-l, where the values for M_(l) andP_(l) can be the same or different and the values for N_(l) and Q_(l)can be the same or different. At those who are skilled in the art willappreciate, one or more of the M_(l) microphones at location 310-l canbe assigned to a particular audio input channel at bridge 304, while oneor more of the N_(l) loudspeakers at location 310-l can be assigned to aparticular audio output channel. Bridge 304 keeps track of the P-to-Qrelationship for each pair of teleconference locations and maps thechannels accordingly.

As those who are skilled in the art will appreciate, after reading thisspecification, the value for M_(l) across two or more endpoints can bethe same or different and the value for N_(l) can be the same ordifferent. Furthermore, the value for P_(l) across two or more endpointscan be the same or different and the value for Q_(l) can be the same ordifferent.

At task 1003, bridge 304 adjusts one or more transfer functions thatgovern the output signals to be transmitted during a conference call tothe endpoints, based on the determined audio channels and the relativepositions of the endpoints across teleconference locations. As part ofthis task, the mapping is established between each sound field at onelocation to the corresponding sound field at each other location. Forexample, for a three-channel system, bridge 304 transmits the signalsfrom microphone channel “A” in the first sound field to loudspeakerchannel “A” in the second sound field, the signals from microphonechannel B to loudspeaker channel B, and the signals from microphonechannel C to loudspeaker channel C. Bridge 304 ensures that the firstsound field represented as microphone channels A-B-C is mimicked in thesecond sound field as “A-B-C”, and not as “A-C-B”. As those who areskilled in the art will appreciate, the same process applies in theother direction, in which the second sound field is represented inmulti-channel audio for the listeners in the first sound field.

There can be a different number of input channels from one location thanthere are output channels to another location. When P₁>Q₂, bridge 304mixes the audio from the “extra” input channel into one or more of theoutput channels. When P₁<Q₂, bridge 304 synthesizes an “extra” outputchannel's audio from one or more of the input channels.

In some embodiments, bridge 304 adjusts the one or more transferfunctions to provide cross-channel mixing to coax the other channel'sspeakerphone into the receive state, for the purpose of controllingecho. For example, for teleconference location 301-4 with each of twoindependent speakerphones (i.e., endpoints 301-9 and 301-10) receiving adifferent output audio channel (i.e., “A” and “B”), bridge 304 canprovide an attenuated version of the signal being fed to channel A alsoto channel B, or vice-versa.

FIG. 11 depicts a flowchart of the salient subtasks that are related todetermining acoustic collocation, as part of task 602, in accordancewith the illustrative embodiment of the present invention.

At task 1101, bridge 304 selects endpoints 301-1 through 301-J to beevaluated. The actual endpoints that are to be evaluated are based onthe determination made earlier as to which endpoints are part of theconference call.

At task 1102, bridge 304 initializes endpoint pointer j to 1.

At task 1103, bridge 304 determines which endpoints are acousticallycollocated with endpoint 301-j and accordingly adjusts the mixertransfer function that corresponds to the output signal to endpoint301-j. Task 1103 is described below and with respect to FIG. 14.

At task 1104, bridge 304 increments pointer j.

At task 1105, bridge 304 determines whether acoustic collocation hasbeen determined for all J selected endpoints being evaluated. If allendpoints have been checked, task execution proceeds to task 603.Otherwise, task execution proceeds back to task 1103.

FIG. 12 depicts a flowchart of the salient subtasks that are related toadapting to cell phones or other endpoints that enter or leave a soundfield, as part of task 605, in accordance with the illustrativeembodiment of the present invention.

At task 1201, bridge 304 identifies and determines the characteristicsof each endpoint of interest—that is, each endpoint that is capable ofappearing in, moving in, or disappearing from the sound field in whichit is present. For example, the endpoint might be a cell phone or otherwireless telephone. The endpoints of interest can be identified tobridge 304 by a conference call participant, by private branch exchange302, or through some other means. In accordance with the illustrativeembodiment, bridge 304 queries exchange 302 about a particular endpointthat is dialing into the conference call, to which exchange 302 mightrespond by identifying the endpoint as that of an employee and as beinga cell phone in terminal type. In some embodiments, bridge 304additionally determines one or more other characteristics of theendpoint.

At task 1202, bridge 304 monitors whether the endpoint of interest isacoustically collocated with one or more other endpoints. In accordancewith the illustrative embodiment, bridge 304 infers collocation bytracking the geo-location of the endpoint and comparing the endpoint'sgeo-location with the geo-locations of one or more conference telephoneswhose geo-locations have been predetermined and stored in a databaseaccessible by the bridge. It will be clear to those skilled in the arthow to determine and store the geo-location of one or more cell phones.When the cell phone comes within a predetermined distance from theconference telephone, as determined from the difference in theirgeo-locations, bridge 304 infers that the cell phone and conferencetelephone have become collocated.

It will be clear to those skilled in the art, in some alternativeembodiments, how to determine acoustic collocation through other means.For example, the tasks described below and with respect to FIG. 14 canbe adapted to acoustically determine collocation of a cell phone with aconference telephone.

At task 1203, bridge 304 determines whether to exclude at least acomponent of a signal from an output signal (i.e., a signal to betransmitted to one of the endpoints in a conference call). For example,when it is determined that a cell phone is acoustically collocated witha conference telephone, bridge 304 will exclude some or all of thesignal received from the cell phone from the signal to be transmitted tothe conference telephone, in order to prevent feedback.

At task 1204, bridge 304 determines whether to refrain from transmittinga signal to the endpoint of interest. In accordance with theillustrative embodiment, bridge 304 concludes that an endpoint is beingused as a satellite microphone when the endpoint i) is a cell phone, asdetermined earlier, and ii) either is not moving and/or is within apredetermined distance from (or acoustically collocated with) theconference telephone. In this case, there would be no need to provide anaudio signal to the cell phone since no one is using the cell phone tolisten. In some embodiments, bridge 304 can determine that a cell phoneis not moving by comparing successive geo-location measurements of thephone. In some alternative embodiments, bridge 304 bases the decision torefrain on a predetermined characteristic of a signal that is used todetermine acoustic collocation, such as audio level.

Conversely, when bridge 304 determines that the endpoint of interest ismoving away from the collocated conference phone, the bridge can resumetransmitting an audio signal to the endpoint.

At task 1205, bridge 304 adjusts the mixer transfer function for eachoutput channel, based on one or more of the other subtasks thatconstitute task 605. Task execution then proceeds to task 606.

FIG. 13 depicts a flowchart of the salient subtasks that are related toacoustically determining the presence of endpoints, as part of task1001, in accordance with the illustrative embodiment of the presentinvention.

As part of the tasks that are described here with respect to FIG. 13,bridge 304 plays a special audio signal (e.g., a tone, etc.) out of theloudspeaker of each endpoint 301-1 through 301-J. While each tone isplayed out, bridge 304 listens through the microphones of the otherphones. Bridge 304 then correlates the received audio signals with thosegenerated by the bridge. By initializing in this way, bridge 304 is ableto determine which of the M_(L) microphones and N_(L) loudspeakers areat each of teleconference locations 310-1 through 310-L (i.e., aretogether in the same sound field), as well as their relative positionsat each location.

At task 1301, bridge 304 initializes endpoint pointer j to 1.

At task 1302, bridge 304 transmits a predetermined signal x₀ to endpoint301-j. As those who are skilled in the art will appreciate, afterreading this specification, signal x₀'s characteristics (e.g., audiolevel, frequency, duty cycle, etc.) are selected to allow otherendpoints to detect the played signals when those endpoints areproximate to endpoint 301-j.

At task 1303, bridge 304 receives signals from one or more endpoints,including audio signals being detected by the microphones at theendpoints. The audio signals might comprise predetermined signal x₀ thatis being played from endpoint 301-j's loudspeaker at the teleconferencelocation currently being assessed.

At task 1304, bridge 304 determines the amount of correlation betweenpredetermined signal x₀ (i.e., the signal being transmitted at endpoint301-j) and each signal received from one or more of the other endpoints.

At task 1305, bridge 304 increments endpoint pointer j.

At task 1306, bridge 304 determines whether all J endpoints have beenevaluated. If they have all been evaluated, task execution proceeds totask 1307. Otherwise, task execution proceeds back to task 1302.

At task 1307, bridge 304 determines which endpoints are at eachteleconference location, based on the signals received at task 1303 foreach endpoint 301-j. In accordance with the illustrative embodiment,bridge 304 examines the signal strength of each received signal andcompares the signal strength to a predetermined threshold. If the signalstrength exceeds the threshold, the corresponding endpoint is determinedto be present at the same teleconference location as endpoint 301-j thatplayed the signal via its loudspeaker. As those who are skilled in theart will appreciate, a property of the received signals other thansignal strength, such as the amount of correlation, can be used todetermine the presence of endpoints at each teleconference location.

At task 1308, bridge 304 determines the relative positions of endpoints301-1 through 301-J, based on the amounts of correlation between thesignals transmitted at task 1302 and the corresponding signals receivedat task 1303. In accordance with the illustrative embodiment, bridge 304examines a characteristic of the correlation between the transmittedsignal and each received signal, as determined at task 1304, andcompares the correlation to one or more predetermined thresholds.Depending on which thresholds are exceeded by which received signals,bridge 304 infers relative positions between each endpoint that detectsa signal and endpoint 301-j that played the transmitted signal. Bridge304 then infers additional information about the relative positions byperforming the threshold test on the other sets of signal correlationsthat correspond to other received signals compared against the signalsplayed from other endpoints at the same teleconference location. Asthose who are skilled in the art will appreciate, a property of thereceived signals other than the amount of correlation can be used todetermine the relative positions of the endpoints at each teleconferencelocation.

After task 1308, task execution proceeds to task 1002.

FIG. 14 depicts a flowchart of the salient subtasks that are related todetermining which endpoints are acoustically collocated with endpoint301-j, as part of task 1103, in accordance with the illustrativeembodiment of the present invention. Determining acoustic collocation isimportant when two or more endpoints—for example, cell phone 301-4 andconference phone 301-5—are at the same conferencing location; thecollocated endpoints need not receive each other's audio, since theparticipants are in the same sound field and can hear each otherdirectly.

As part of the tasks that are described here with respect to FIG. 14,bridge 304 plays a special audio signal (e.g., a tone, etc.) out ofendpoint 301-j's loudspeaker. While the tone is played out, bridge 304listens through the microphones of the other phones being evaluated withrespect to endpoint 301-j. Bridge 304 then determines whether thereceived audio signals are sufficiently correlated with the tonegenerated by the bridge. In accordance with the illustrative embodiment,bridge 304 performs the described tasks before the conference callstarts. However, it will be clear to those skilled in the art, afterreading this specification, how to make and use embodiments of thepresent invention in which the determination of whether some signals aresufficiently correlated—or the determination of acoustic collocation ingeneral—is performed during the conference call.

Although the tasks described here evaluate all endpoints with respect toeach endpoint 301-j, it will be clear to those skilled in the art how toevaluate only a subset of the endpoints on a conference call, for eachendpoint 301-j. For example, once the endpoints at each teleconferencelocation have been determined, it might be advantageous to evaluate onlythose endpoints at the same teleconference location as endpoint 301-j.

Moreover, in accordance with the illustrative embodiment, the audiosignal for determining collocation is transmitted to the endpoints oneendpoint at a time. However, it will be clear to those skilled in theart, after reading this specification, how to make and use embodimentsof the present invention in which the audio signals are transmitted tomultiple endpoints concurrently in order to identify multiple sets ofcollocated endpoints concurrently. For example, those transmitted audiosignals can be formed so that they will not interfere with each other(i.e., they are acoustically orthogonal with respect to each other).

At task 1401, bridge 304 transmits a predetermined signal x_(j) toendpoint 301-j. As those who are skilled in the art will appreciate,after reading this specification, signal x_(j)'s characteristics (e.g.,level, frequency, duty cycle, etc.) are selected to allow otherendpoints to pick up the played signals, when those endpoints areproximate to endpoint 301-j.

At task 1402, bridge 304 initializes endpoint pointer k to 1.

At task 1403, bridge 304 receives a signal s_(k) from endpoint 301-k,when k is not equal to j, including audio signals being picked up byendpoint 301-k's microphone. The audio signals might comprisepredetermined signal x_(j) that is being transmitted from endpoint301-j's loudspeaker at the teleconference location currently beingassessed.

At task 1404, bridge 304 determines the amount of correlation betweenreceived signal s_(k) and predetermined signal x_(j) (i.e., the signalbeing transmitted at endpoint 301-j). In accordance with theillustrative embodiment, bridge 304 compares the correlation to apredetermined threshold; if the correlation amount exceeds thethreshold, received signal s_(k) is considered to be sufficientlycorrelated with signal x_(j).

At task 1405, bridge 304 checks whether signal s_(k) is sufficientlycorrelated with signal x_(j). If there is sufficient correlation, taskexecution proceeds to task 1406. Otherwise, task execution proceeds totask 1407.

At task 1406, bridge 304 adjusts the mixer transfer function thatcorresponds to the output signals to be transmitted to endpoint 301-j,to exclude at least a component of a signal received from endpoint301-k.

At task 1407, bridge 304 increments endpoint pointer k.

At task 1408, bridge 304 determines whether all endpoints have beenevaluated. If they have all been evaluated, task execution proceeds totask 603. Otherwise, task execution proceeds back to task 1403.

In accordance with the illustrative embodiment, acoustic collocation isdetermined acoustically, as described with respect to FIG. 14. It willbe clear to those skilled in the art, after reading this specification,how to determine acoustic collocation through non-acoustic means—forexample, by applying the technique of using geo-location measurementsthat is described above and with respect to task 1202.

It is to be understood that the disclosure teaches just one example ofthe illustrative embodiment and that many variations of the inventioncan easily be devised by those skilled in the art after reading thisdisclosure and that the scope of the present invention is to bedetermined by the following claims.

1. A method comprising: establishing, at a teleconference bridge, afirst teleconference call that involves at least a first endpointassigned to a first port, a second endpoint assigned to a second port,and a third endpoint assigned to a third port, wherein first endpoint iscapable of having a telephone call independently of the teleconferencebridge, and wherein the second endpoint and the third endpoint areacoustically isolated from each other; receiving, at the teleconferencebridge, a first receive audio signal s₁ from the first endpoint via thefirst port, a second receive audio signal s₂ from the second endpointvia the second port, and a third receive audio signal s₃ from the thirdendpoint via the third port; determining whether to transmit any audiosignal that is based on at least one of the signal s₂ and the signal s₃to the first endpoint, based on i) the terminal type of the firstendpoint, ii) whether the first endpoint is acoustically collocated withthe second endpoint, and iii) whether the first endpoint is acousticallycollocated with the third endpoint; and transmitting a first transmitaudio signal x₁ to the third endpoint, wherein the signal x₁ is based onat least one of the signal s₁ and the signal s₂.
 2. The method of claim1 further comprising transmitting a second transmit signal x₂ to thesecond endpoint, wherein the signal x₂ is based on the signal s₃, andwherein at least a component of the signal s₁ is excluded from thesignal x₂ when the first endpoint is acoustically collocated with thesecond endpoint.
 3. The method of claim 2 wherein the first endpointcomprises cellular telephone functionality and the second endpoint is aconference telephone.
 4. The method of claim 3 further comprising:transmitting, from the teleconference bridge, a third transmit audiosignal x₃ to the second endpoint; receiving a fourth receive audiosignal s₄ from the first endpoint; and determining that the signal s₄ issufficiently correlated with the signal x₃ and, as a result, that thefirst endpoint is acoustically collocated with the second endpoint. 5.The method of claim 1 wherein the second endpoint and the third endpointare determined to be acoustically isolated from each other, based oncomparing the identifier of the second endpoint and the identifier ofthe third endpoint to a database of endpoints.
 6. A method comprising:monitoring whether a first endpoint is acoustically collocated with asecond endpoint, by comparing one or more geo-location values of thefirst endpoint with a geo-location value of the second endpoint, whereinthe first endpoint is capable of having a telephone call independentlyof a teleconference bridge and is capable of moving into or out frombeing acoustically collocated with the second endpoint; receiving, atthe teleconference bridge, a first receive audio signal s₁ from thefirst endpoint via a first port, a second receive audio signal s₂ fromthe second endpoint via a second port, and a third receive audio signals₃ from a third endpoint via a third port, wherein the first endpoint,the second endpoint, and the third endpoint are part of a firstconference call that is handled by the teleconference bridge;transmitting, from the teleconference bridge, a first transmit audiosignal x₁ to the third endpoint and a second transmit audio signal x₂ tothe second endpoint, wherein the signal x₁ is based on at least one ofsignal s₁ and signal s₂, and wherein signal x₂ is based on at least oneof the signal s₁ and the signal s₃; and when the first endpoint isacoustically collocated with the second endpoint, excluding at least acomponent of the signal s₁ from the signal x₂.
 7. The method of claim 6wherein the first endpoint comprises cellular telephone functionalityand the second endpoint is a conference telephone.
 8. The method ofclaim 7 further comprising, when the first endpoint is acousticallycollocated with the second endpoint, refraining from transmitting anyaudio signals to the first endpoint during at least a first portion ofthe first conference call.
 9. The method of claim 8 wherein therefraining is based on a predetermined characteristic of a fourthreceive audio signal s₄ received from the first endpoint.
 10. The methodof claim 9 wherein the predetermined characteristic is audio level. 11.The method of claim 8 wherein the refraining is based on the spatialproximity of the first endpoint to the second endpoint.
 12. The methodof claim 8 further comprising transmitting a third transmit audio signalx₃ to the first endpoint during a second portion of the first conferencecall, wherein the signal x₃ is based on the signal s₃.
 13. The method ofclaim 6 wherein the second endpoint and the third endpoint aredetermined to be acoustically isolated from each other, based oncomparing the identifier of the second endpoint and the identifier ofthe third endpoint to a database of endpoints.
 14. The method of claim 6wherein the monitoring of whether the first endpoint is acousticallycollocated with the second endpoint further comprises: transmitting,from the teleconference bridge, a third transmit audio signal x₃ to thesecond endpoint; receiving a fourth receive audio signal s₄ from thefirst endpoint; and determining whether the signal s₄ is sufficientlycorrelated with the signal x₃.
 15. A method comprising: monitoringwhether a first endpoint is acoustically collocated with a secondendpoint, wherein the first endpoint comprises cellular telephonefunctionality; receiving, at a teleconference bridge, a first receiveaudio signal s₁ from the first endpoint via a first port and a secondreceive audio signal s₂ from the second endpoint via the second port,wherein the first endpoint and the second endpoint are part of a firstconference call that is handled by the teleconference bridge;transmitting, from the teleconference bridge, a first transmit audiosignal x₁ to a third endpoint that is also part of the conference calland a second transmit audio signal x₂ to the second endpoint, whereinthe signal x₁ is based on at least one of signal s₁ and signal s₂; andwhen the first endpoint is acoustically collocated with the secondendpoint, i) excluding at least a component of the signal s₁ from thesignal x₂ and ii) refraining from transmitting any audio signals to thefirst endpoint during at least a first portion of the first conferencecall.
 16. The method of claim 15 wherein the refraining is based on apredetermined characteristic of a third receive audio signal s₃ receivedfrom the first endpoint.
 17. The method of claim 16 wherein thepredetermined characteristic is audio level.
 18. The method of claim 15wherein the refraining is based on the spatial proximity of the firstendpoint to the second endpoint.
 19. The method of claim 15 furthercomprising transmitting a third transmit audio signal x₃ to the firstendpoint during a second portion of the first conference call.
 20. Themethod of claim 19 wherein the transmitting of the signal x₃ is based ona movement of the first endpoint away from the second endpoint.